The objective of this project is to examine the role of matrix metalloproteinases elaborated by human mononuclear phagocytes in human lung biology. We will study molecular mechanisms of the gene regulation of the alveolar macrophage's two principal metalloproteinases, interstitial collagenase and 92 kDa gelatinase, whose production is controlled by IFN- gamma, IL-4, LPS, and type I collagen in a cell type-specific manner. These agents fail to modify the release of fibroblast-derived metalloproteinases. We will study the biological function and expression of the newly-described metalloproteinase, matrilysin, by human mononuclear phagocytes. This enzyme is capable of degrading insoluble elastin and proteoglycans and is only poorly inhibited by TIMPs. Our finding of extensive matrilysin production by developing mononuclear phagocytes represents the first human cell type associated with this enzyme s expression. We will test the hypothesis that matrilysin is important for the penetration of basement membranes and the traversing of interstitial barriers. We will also study the production of TIMP-2 by human alveolar macrophages, whose biosynthesis we have found is regulated in a completely opposite manner to that of TIMP-1 and interstitial collagenase (i.e., macrophage activators such as LPS markedly induce interstitial collagenase and TIMP-1, but downregulate TIMP-2). The molecular basis for such disparate regulation will be pursued. Our studies will incorporate cell biology, biochemistry, and molecular biologic approaches, including invasion assays, purification of metalloproteinases, elucidation of cis and trans regulatory elements, and in situ hybridization.